Electrodes, in general, are bonded in a semiconductor manufacturing process by using alloys having low melting points, such as lead (Pb), tin (Sn), and bismuth (Bi). The alloys, however, are harmful to human body, and may contaminate semiconductor manufacturing equipments due to low vapor pressure.
Aluminum (Al) is commonly used for a metal electrode in most semiconductor manufacturing processes. In case that an aluminum (Al) electrode is bonded such that two substrates are overlapped having the aluminum (Al) electrode in therebetween, the aluminum (Al) electrode may be heated near to its melting point. Due to the heating of the aluminum (Al) electrode, remaining regions of the aluminum (Al) electrode, which are not bonding areas, also melt, which in turn has an adverse effect on existing wires or circuits of the substrates.